Cégep de Thetford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cégep de Thetford clear sky chart from 2005-11-06 to 2024-01-27.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
24%
22798
11%
75084
6%
22751
30%
22751
12%
56619

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 10thNight
9%
760
7%
2649
2%
757
14%
757
4%
2267
January11th to 20thNight
11%
760
7%
2660
2%
760
17%
760
5%
2218
January21st to endNight
15%
820
8%
2868
3%
820
22%
820
8%
2257
February1st to 10thNight
13%
720
9%
2493
3%
720
21%
720
7%
1994
February11th to 20thNight
10%
703
8%
2100
1%
700
19%
700
7%
1723
February21st to endNight
17%
592
14%
1776
6%
592
28%
592
12%
1371
March1st to 10thNight
15%
720
13%
2160
5%
720
25%
720
11%
1683
March11th to 20thNight
17%
720
13%
2072
4%
720
26%
720
11%
1607
March21st to endNight
25%
792
17%
2044
6%
792
32%
792
17%
1545
April1st to 10thNight
20%
720
12%
1800
4%
720
25%
720
14%
1405
April11th to 20thNight
25%
637
16%
1701
6%
637
31%
637
19%
1227
April21st to endNight
22%
540
14%
1620
7%
540
28%
540
13%
1203
May1st to 10thNight
24%
530
13%
1610
7%
530
32%
530
16%
1181
May11th to 20thNight
30%
354
17%
1416
14%
354
41%
354
13%
940
May21st to endNight
28%
389
11%
1551
10%
388
38%
388
15%
1019
June1st to 10thNight
30%
360
8%
1324
7%
360
36%
360
14%
952
June11th to 20thNight
38%
360
13%
1260
13%
360
45%
360
19%
832
June21st to endNight
34%
360
8%
1323
8%
360
39%
360
15%
943
July1st to 10thNight
40%
350
10%
1400
12%
350
47%
350
17%
912
July11th to 20thNight
43%
348
11%
1392
15%
348
48%
348
18%
894
July21st to endNight
43%
394
11%
1486
14%
372
45%
372
16%
1003
August1st to 10thNight
51%
368
14%
1432
13%
366
55%
366
20%
908
August11th to 20thNight
44%
532
13%
1596
8%
532
48%
532
20%
1120
August21st to endNight
41%
718
17%
1906
8%
718
45%
718
25%
1307
September1st to 10thNight
39%
720
12%
1800
4%
720
42%
720
26%
1272
September11th to 20thNight
43%
720
17%
1962
9%
720
48%
720
27%
1308
September21st to endNight
36%
720
18%
1980
11%
720
42%
720
24%
1355
October1st to 10thNight
33%
720
19%
1980
11%
720
40%
720
20%
1425
October11th to 20thNight
26%
720
12%
2296
6%
720
33%
720
13%
1716
October21st to endNight
18%
792
10%
2574
4%
792
26%
792
11%
1985
November1st to 10thNight
19%
740
11%
2407
6%
740
26%
740
11%
1811
November11th to 20thNight
21%
760
14%
2470
9%
760
29%
760
11%
1897
November21st to endNight
17%
800
10%
2707
5%
800
23%
800
8%
2164
December1st to 10thNight
12%
850
5%
2850
1%
850
16%
850
5%
2417
December11th to 20thNight
13%
850
7%
3494
3%
848
18%
848
4%
2930
December21st to endNight
8%
859
6%
4925
1%
845
15%
845
3%
3828

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
19%12%5%8%7%35%45%6%26%
74661
Night
18%13%5%9%7%35%445%27%
75371
TransparencyDay
59%5%10%17%8%1
74366
Night
59%6%10%17%8%1
75201
SeeingDay
28%17%29%17%7%2
13986
Night
26%15%28%22%8%1
22807

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
15%18%10%15%9%46%43412%
1517
11th to 20thDay
15%19%8%12%9%4433320%
1520
21st to endDay
10%13%8%11%11%47%5%45%22%
1632
February1st to 10thDay
12%19%8%13%10%5%6%43416%
1464
11th to 20thDay
14%19%9%12%8%45%5%45%16%
1748
21st to endDay
13%18%7%11%8%35%5%45%20%
1480
March1st to 10thDay
14%15%6%10%9%4435%5%25%
1797
11th to 20thDay
17%15%7%8%6%3444427%
1887
21st to endDay
17%14%6%9%9%2444427%
2309
April1st to 10thDay
22%15%5%8%8%34335%24%
2160
11th to 20thDay
20%12%46%5%34445%34%
2208
21st to endDay
22%14%47%6%34446%26%
2340
May1st to 10thDay
22%10%5%6%6%35%35%5%30%
2366
11th to 20thDay
21%9%37%5%35%45%7%31%
2478
21st to endDay
21%8%37%6%46%6%6%7%27%
2725
June1st to 10thDay
25%8%36%6%45%5%5%8%26%
2630
11th to 20thDay
20%6%25%6%35%6%6%9%31%
2700
21st to endDay
25%8%48%6%445%5%6%25%
2630
July1st to 10thDay
17%8%37%6%45%6%6%8%31%
2520
11th to 20thDay
18%7%46%6%45%5%7%8%30%
2520
21st to endDay
21%8%35%5%36%6%6%9%29%
2744
August1st to 10thDay
21%7%28%7%45%5%6%9%25%
2477
11th to 20thDay
18%8%36%6%35%5%6%7%31%
2304
21st to endDay
19%7%35%6%45%5%6%7%33%
2448
September1st to 10thDay
18%8%36%5%45%5%5%7%34%
2160
11th to 20thDay
21%7%25%42446%6%39%
1998
21st to endDay
20%7%35%5%345%6%9%34%
1980
October1st to 10thDay
23%11%35%5%2445%7%30%
1980
11th to 20thDay
23%15%48%6%45%45%5%23%
1661
21st to endDay
26%18%5%8%6%2434419%
1782
November1st to 10thDay
19%16%48%6%34435%28%
1671
11th to 20thDay
19%16%7%11%7%33445%21%
1710
21st to endDay
19%19%7%10%7%35%445%18%
1466
December1st to 10thDay
20%22%8%12%8%3324315%
1330
11th to 20thDay
20%17%8%10%6%4433321%
1668
21st to endDay
22%20%7%12%9%3432315%
2651
January1st to 10thNight
14%19%8%15%10%46%33314%
2649
11th to 20thNight
15%17%8%13%10%45%43417%
2660
21st to endNight
10%14%6%12%10%5%7%5%5%5%20%
2868
February1st to 10thNight
12%16%7%11%11%47%44420%
2493
11th to 20thNight
12%18%7%13%7%46%44421%
2098
21st to endNight
13%15%7%10%8%45%44427%
1776
March1st to 10thNight
14%14%6%9%8%46%45%425%
2150
11th to 20thNight
15%14%5%9%7%35%5%4428%
2071
21st to endNight
17%11%49%6%45%44432%
2044
April1st to 10thNight
22%13%48%5%25%5%45%27%
1800
11th to 20thNight
19%9%36%6%3445%6%34%
1701
21st to endNight
23%11%46%5%35%45%5%30%
1620
May1st to 10thNight
23%9%37%5%3445%6%31%
1610
11th to 20thNight
18%9%36%6%25%5%47%35%
1415
21st to endNight
21%7%36%5%3446%7%35%
1550
June1st to 10thNight
23%9%36%5%35%6%47%29%
1324
11th to 20thNight
19%6%35%5%35%5%6%7%36%
1260
21st to endNight
21%7%37%6%35%6%5%8%30%
1323
July1st to 10thNight
15%6%36%6%37%5%6%8%36%
1440
11th to 20thNight
14%7%45%6%36%6%7%7%36%
1440
21st to endNight
16%7%36%6%35%6%6%8%36%
1574
August1st to 10thNight
17%5%245%35%47%10%38%
1442
11th to 20thNight
17%8%36%6%345%6%7%35%
1596
21st to endNight
17%6%36%5%3436%7%42%
1906
September1st to 10thNight
19%6%36%5%25%45%7%39%
1800
11th to 20thNight
17%7%344245%45%45%
1962
21st to endNight
18%7%25%434447%41%
1980
October1st to 10thNight
19%8%35%5%3445%7%36%
1980
11th to 20thNight
22%11%36%6%45%45%6%28%
2296
21st to endNight
25%14%5%7%6%3445%424%
2574
November1st to 10thNight
20%15%5%7%5%4445%5%27%
2407
11th to 20thNight
18%12%6%10%7%4444426%
2470
21st to endNight
17%17%7%11%8%34445%22%
2707
December1st to 10thNight
21%19%8%11%8%3434414%
2850
11th to 20thNight
19%17%8%14%8%4434417%
3531
21st to endNight
21%22%6%10%6%2332321%
5004

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
77%46%9%4
1518
11th to 20thDay
72%36%13%5%1
1520
21st to endDay
64%48%14%8%2
1632
February1st to 10thDay
73%36%10%6%1
1464
11th to 20thDay
73%38%9%7%1
1757
21st to endDay
66%47%15%6%2
1480
March1st to 10thDay
63%48%14%10%2
1800
11th to 20thDay
62%39%14%11%1
1887
21st to endDay
62%47%15%10%2
2309
April1st to 10thDay
64%49%13%8%2
2160
11th to 20thDay
54%410%20%12%2
2208
21st to endDay
61%48%14%10%2
2340
May1st to 10thDay
56%5%8%16%13%2
2366
11th to 20thDay
53%5%11%19%11%1
2482
21st to endDay
55%7%10%17%11%
2725
June1st to 10thDay
56%7%10%19%7%1
2630
11th to 20thDay
49%7%13%21%10%1
2700
21st to endDay
59%7%9%16%8%
2630
July1st to 10thDay
49%9%13%22%6%
2450
11th to 20thDay
50%8%15%21%7%
2445
21st to endDay
52%8%13%20%6%
2591
August1st to 10thDay
55%8%15%19%3
2463
11th to 20thDay
50%8%14%19%9%
2304
21st to endDay
49%6%14%22%10%
2448
September1st to 10thDay
48%7%14%21%9%1
2160
11th to 20thDay
45%5%12%26%12%
1998
21st to endDay
46%8%13%23%10%
1980
October1st to 10thDay
54%5%11%22%8%
1980
11th to 20thDay
64%6%12%15%3
1661
21st to endDay
69%48%14%5%1
1782
November1st to 10thDay
60%5%10%17%7%
1671
11th to 20thDay
66%5%9%13%6%1
1710
21st to endDay
70%6%10%11%3
1466
December1st to 10thDay
76%37%9%4
1330
11th to 20thDay
70%46%13%7%
1668
21st to endDay
76%449%5%1
2651
January1st to 10thNight
76%36%10%4
2649
11th to 20thNight
72%5%6%10%6%1
2660
21st to endNight
65%5%9%12%7%1
2868
February1st to 10thNight
67%48%12%7%1
2493
11th to 20thNight
69%47%11%7%1
2100
21st to endNight
62%47%14%11%2
1776
March1st to 10thNight
62%5%8%16%8%1
2160
11th to 20thNight
59%6%8%12%12%2
2072
21st to endNight
56%49%18%10%3
2044
April1st to 10thNight
60%49%14%11%2
1800
11th to 20thNight
50%6%10%20%12%2
1701
21st to endNight
56%5%10%16%11%2
1620
May1st to 10thNight
55%5%9%16%14%2
1610
11th to 20thNight
50%6%9%19%14%1
1416
21st to endNight
48%6%12%21%12%1
1551
June1st to 10thNight
53%7%12%19%8%
1324
11th to 20thNight
47%6%9%24%12%2
1260
21st to endNight
53%7%12%19%8%
1323
July1st to 10thNight
44%9%16%22%8%
1400
11th to 20thNight
44%8%17%22%9%
1392
21st to endNight
47%9%14%21%8%
1486
August1st to 10thNight
41%9%17%27%5%
1432
11th to 20thNight
46%9%16%21%7%
1596
21st to endNight
42%7%13%27%10%
1906
September1st to 10thNight
45%7%14%24%9%1
1800
11th to 20thNight
41%7%14%29%9%1
1962
21st to endNight
43%8%11%25%13%1
1980
October1st to 10thNight
49%7%9%22%13%
1980
11th to 20thNight
57%6%12%20%5%
2296
21st to endNight
62%5%11%13%8%
2574
November1st to 10thNight
59%6%12%17%6%1
2407
11th to 20thNight
62%411%14%8%1
2470
21st to endNight
66%5%10%14%5%
2707
December1st to 10thNight
74%49%9%3
2850
11th to 20thNight
72%5%6%10%6%
3532
21st to endNight
70%37%14%6%
5004

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
32%20%36%11%2
180
11th to 20thDay
34%24%29%11%2
180
21st to endDay
24%28%31%15%21
188
February1st to 10thDay
40%25%26%6%21
179
11th to 20thDay
31%26%32%9%1
416
21st to endDay
33%23%26%15%3
346
March1st to 10thDay
28%23%31%14%4
420
11th to 20thDay
32%23%27%13%41
420
21st to endDay
31%23%27%12%7%1
462
April1st to 10thDay
38%20%24%11%5%2
420
11th to 20thDay
34%20%25%14%6%1
412
21st to endDay
34%22%26%12%42
420
May1st to 10thDay
34%16%30%14%41
423
11th to 20thDay
26%15%32%19%6%2
447
21st to endDay
24%21%34%14%6%1
485
June1st to 10thDay
31%15%30%16%8%1
560
11th to 20thDay
22%15%28%24%11%1
630
21st to endDay
25%13%31%21%9%2
560
July1st to 10thDay
21%11%31%28%8%1
445
11th to 20thDay
19%12%41%20%9%
444
21st to endDay
24%9%34%25%7%1
488
August1st to 10thDay
24%13%29%22%11%2
446
11th to 20thDay
22%9%30%27%11%2
439
21st to endDay
25%13%25%19%11%6%
495
September1st to 10thDay
21%15%29%22%8%5%
450
11th to 20thDay
25%12%23%23%12%4
450
21st to endDay
22%17%25%21%10%5%
450
October1st to 10thDay
26%17%27%18%10%3
450
11th to 20thDay
32%16%28%16%8%1
378
21st to endDay
40%18%22%16%31
396
November1st to 10thDay
34%16%29%16%4
365
11th to 20thDay
29%21%26%16%7%1
370
21st to endDay
35%21%30%12%1
214
December1st to 10thDay
37%17%27%13%41
180
11th to 20thDay
37%24%26%10%3
180
21st to endDay
36%23%28%11%21
198
January1st to 10thNight
28%22%32%15%21
760
11th to 20thNight
29%22%30%14%5%
760
21st to endNight
20%20%35%20%41
820
February1st to 10thNight
22%24%32%17%4
720
11th to 20thNight
26%21%34%15%3
703
21st to endNight
26%17%33%19%5%
592
March1st to 10thNight
25%18%36%18%3
720
11th to 20thNight
26%22%31%17%41
720
21st to endNight
25%16%27%25%5%1
792
April1st to 10thNight
32%16%27%19%5%
720
11th to 20thNight
27%15%30%22%7%
637
21st to endNight
31%16%27%20%6%
540
May1st to 10thNight
28%13%28%24%6%1
530
11th to 20thNight
23%8%31%30%5%1
354
21st to endNight
23%8%34%26%7%1
389
June1st to 10thNight
26%12%26%28%8%1
360
11th to 20thNight
22%8%25%33%12%
360
21st to endNight
22%8%30%29%11%1
360
July1st to 10thNight
15%6%32%34%12%1
350
11th to 20thNight
15%6%27%39%13%1
348
21st to endNight
18%7%24%41%10%
394
August1st to 10thNight
19%421%38%18%1
368
11th to 20thNight
19%7%23%33%17%1
532
21st to endNight
21%7%23%29%16%3
718
September1st to 10thNight
21%8%26%30%13%2
720
11th to 20thNight
22%8%23%28%18%2
720
21st to endNight
23%9%28%25%14%1
720
October1st to 10thNight
24%12%27%25%10%1
720
11th to 20thNight
28%15%25%21%9%2
720
21st to endNight
35%16%26%19%4
792
November1st to 10thNight
30%17%26%21%5%
740
11th to 20thNight
28%18%27%17%10%1
760
21st to endNight
31%19%26%18%5%1
800
December1st to 10thNight
34%19%26%15%5%
850
11th to 20thNight
30%23%25%17%5%1
850
21st to endNight
36%20%25%14%4
868
Page generated at 2024-01-24 09:37:31. Version ac07

Copyright 2024 Attilla Danko


Cégep de Thetford Clear Sky Chart |Charts Home